Microlithography is used in the fabrication of microstructured components like integrated circuits, LCD's and other microstructured devices. The microlithographic process is performed in a so-called microlithographic exposure system including an illumination system and a projection lens. The image of a mask (or reticle) being illuminated by the illumination system is projected, through the projection lens, onto a resist-covered substrate, typically a silicon wafer bearing one or more light-sensitive layers and being provided in the image plane of the projection lens, in order to transfer the circuit pattern onto the light-sensitive layers on the wafer.
The generalized description of the propagation of polarized light through the projection lens uses complex electromagnetic transfer functions like Jones pupils, Mueller matrices or Stokes parameters. Nevertheless, Geh, B., et al., “The impact of projection lens polarization properties on lithographic process at hyper-NA” in Optical Microlithography XX. 2007. USA: SPIE-Int. Soc. Opt. Eng. Vol 6520, p. 6520-15, showed that in current lithography lenses these transfer functions can be simplified to pupil maps corresponding to the basic physical effects of apodization, retardation and diattenuation. The so-called Zernike expansion of the scalar projection lens aberrations has been successfully introduced to provide the basis for a better understanding, control, and reduction of aberration induced imaging errors. In certain optical systems, the scalar Zernike polynomials provide a convenient base set.